Filter

  • Filter = a device that can reduce or enhance certain aspects of an (input) signal

    See: click here

  • AND gates and OR gates can work as an all or nothing filter

    We can use AND gates (or OR gates) to:

      1. Allow an input signal to pass the AND gate (or OR gate)

      2. Block an input signal from passing the AND gate (or OR gate)      

The AND gate as an all-or-nothing filter
 

Traditional view of the AND gate:

 

The AND gate as an all-or-nothing filter
 

A different way to view the operation of the AND gate:

The signal b controls whether the input a is allowed to pass to the output

The AND gate as an all-or-nothing filter
 

A different way to view the operation of the AND gate:

When the signal b = 1, the input signal is allowed to pass the AND gate (filter)

The AND gate as an all-or-nothing filter
 

A different way to view the operation of the AND gate:

When the signal b = 0, the input signal is blocked

The AND gate as an all-or-nothing filter
 

Typical usages of the AND gate as filter:

The input binary number a3a2a1a0 is filtered by the signal b.

The AND gate as an all-or-nothing filter

How to use an AND gate as an all-or-nothing filter:

 
  • The top left column is the input (binary) number 1101
  • The lower left signal controls the filter function: 1 = pass

The AND gate as an all-or-nothing filter

How to use an AND gate as an all-or-nothing filter:

 
  • The top left column is the input (binary) number 1101
  • The lower left signal controls the filter function: 0 = block

The AND gate as an all-or-nothing filter

How to use an AND gate as an all-or-nothing filter:

 
  • DEMO: /home/cs355001/demo/circuits/and-filter  

Multiple controls with AND filter
 

We can have miltiple control signals with the AND gate as filter:

Output = a if and only if all control signals are equal to 1